A longitudinal study of two hundred infants and young children growing up in alternative family styles (single mother households, social contract - rather than legal marriages, and living groups) and a comparison group of infants being raised in nuclear 2-parent families is moving into its third year. The general aims of the study are (1) to document socialization practices in the varying family structures represented; (2) to assess impact on the physical, cognitive and socio- emotional aspects of growth and development through the first six years of life; and (3) to study the differential effects of ideology and value-systems, and certain ecological and social milieu characteristics in the family on child development. All participants come from Caucasian, middle class or stable working-class backgrounds, and are having their 1st or 2nd child. Modes for assessing the family environment include parent interviews, field studies of home and family milieus, observational studies in the home, and semi-structured laboratory observations in project offices. Child development is assessed through standardized neurological and pediatric tests, intelligence tests, and measures of social and emotional behaviors. All participants have been studied beginning with the last trimester of pregnancy. To date, 6 children remain unborn, 153 have reached 6-months of age, and 68 are one year or more. Bibliographic references: Eidusion B., & Alexander, J. Emergent family styles and the role of women. In Rose, C. (Ed.), Meeting women's needs. New York: Jossey Bass, 1975; Eiduson, B., Cohen, J. & Alexander, J. Alternatives in child rearing in the 1970's. Reprinted in Clarke, J. (Ed.), Intimacy, marriage and the family. New York: Allyn and Bacon, 1975.